Hydrocarbon conversion processes often employ multiple reaction zones through which hydrocarbons pass in a series flow. Each reaction zone in the series often has a unique set of design requirements. A minimum design requirement of each reaction zone in the series is the hydraulic capacity to pass the desired throughput of hydrocarbons. An additional design requirement of each reaction zone is sufficient heating to perform a specified degree of hydrocarbon conversion.
One well-known hydrocarbon conversion process is catalytic reforming. Generally, catalytic reforming is a well-established hydrocarbon conversion process employed in the petroleum refining industry for improving the octane quality of hydrocarbon feedstocks. The primary products of reforming are a motor gasoline blending component or aromatics for petrochemicals. Reforming may be defined as the total effect produced by dehydrogenation of cyclohexanes and dehydroisomerization of alkylcyclopentanes to yield aromatics, dehydrogenation of paraffins to yield olefins, dehydrocyclization of paraffins and olefins to yield aromatics, isomerization of n-paraffins, isomerization of alkylcycloparaffins to yield cyclohexanes, isomerization of substituted aromatics, and hydrocracking of paraffins. A reforming feedstock can be a hydrocracker, straight run, FCC, or coker naphtha, and it can contain many other components such as a condensate or thermal cracked naphtha.
Heaters or furnaces are often used in hydrocarbon conversion processes, such as reforming, to heat the process fluid before it is reacted. The heaters can be located before the first reaction zone and/or between reaction zones. Generally, most of the fired heaters or furnaces have a U-tube configuration with end fired burners. The fired heater box typically contains 3 or 4 cells made up of the charge heater and 2 or 3 interheaters. The fired heater cells are typically arranged in row at the same height. However, this arrangement takes up a lot of space, increasing the cost of the plant.
Therefore, there is a need for improved arrangements of fired heaters.